1. Field of the Invention
The present invention relates to an oriented polymer composition article comprising crosslinked rubber particles and a process for preparing such an article. A desirable embodiment of the invention relates to an expanded oriented polymer composition article comprising crosslinked rubber particles.
2. Description of Related Art
Oriented polymer composition articles (OPCs) are gaining market share in construction markets previously occupied almost solely by wood materials. For example, a number of different OPC decking materials are now available for use instead of cedar, redwood, treated pine, or other more historically standard decking materials. High strength and low maintenance are but a few of the desirable characteristics of OPCs that are helping them advance in these markets.
Unfortunately, OPCs are susceptible to scratching and marring that is undesirably visible, particularly in dark colored OPCs. OPCs also tend be undesirably susceptible to fibrillation when cut or exposed to abrasion across fibrils proximate to the OPC's surface. These drawbacks reduce the appeal of OPCs for applications such as decking where cutting is necessary and where scratching, abrasion and/or marring is likely to occur.
Methods for improving scratch and mar resistance of polypropylene polymer compositions include applying a protective layer over the polypropylene polymer in the form of a coating or laminate, incorporating slip additives or small hard particulates, or incorporating silicone based additives. (see, for example, Huber, Gregor; et al.; Additive Approaches to Improve Scratch and mar Resistance in Automotive PP and TPO, Conference presentation at TPOs in Automotive; Geneva, Jun. 21-22, 2005. Reprints available at: http://www.ciba.com/pf/docMDMS.asp?targetlibrary=CHBS_PA_MADS&docnumber=427 1). Applying a coating on a polypropylene article adds considerable complexity to OPC processing by requiring an application step after fabricating the article. Moreover, selection of the coating material and application method requires careful screening and testing to ensure that the coating adheres to polypropylene because if the coating delaminates from the article the scratch and mar resistance is lost. Incorporation of slip agents and hard particulates have not offered a complete solution to scratch and mar resistance, nor fibrillation as Comparative Examples A and C-E herein reveal.
Fibrillation can be reduced by heat treating an OPC surface (see, U.S. provisional application 61/014,131). This process is effective at reducing fibrillation but is generally less effective at reducing the appearance of scratches and mars on an OPC and can actually accentuate the appearance of subsequent scratches and mars. Moreover, with ever increasing energy prices, it is desirable to avoid having to apply heat to an OPC.
It is desirable to have a process for producing an OPC that is scratch and mar resistant without requiring application of a material onto the OPC. Moreover, it is desirable to be able to reduce fibrillation of an OPC without having to apply heat to a surface of the OPC. Yet more desirable is a cavitated OPC with these properties in order to also benefit from low weight.